1. Field of the Invention
The present invention relates to a rubber composition suitable for use as a low fuel consumption tire tread, more specifically it relates to a rubber composition for a low fuel consumption tire tread having the improved heat buildup and wear resistance of the tire, without impairing the wet skid resistance.
2. Description of the Related Art
To meet with social needs for resource saving and energy saving, the rubber industry, in particular the tire industry, has in recent years been engaged in active development of low fuel consumption tires. Development of such low fuel consumption tires requires development of low heat buildup rubber compositions. Recently, numerous inventions have been proposed in this field of art.
For example, Japanese Unexamined Patent Publication (Kokai) No. 55-12133 and Japanese Unexamined Patent Publication (Kokai) No. 56-127650 propose a high vinyl polybutadiene rubber (V-BR), while Japanese Unexamined Patent Publication (Kokai) No. 57-55204 and Japanese Unexamined Patent Publication (Kokai) No. 57-73030 propose high vinyl styrene-butadiene copolymer rubbers (V-SBR). It is stated in these publications that these rubbers have the effect of improvement of the grip and the heat buildup. These V-BR and V-SBR, however, have the problem of a remarkable decrease in the wear resistance. Further, Japanese Unexamined Patent Publication (Kokai) No. 61-141741, Japanese Unexamined Patent Publication (Kokai) No. 61-42552, etc. propose rubber compositions further improve in the heat buildup by modification of the V-SBR, but almost nothing is done to improve the wear resistance. The heat buildup was not sufficiently satisfied the recent needs of low heat buildup. A rubber composition having lower heat buildup and improved wear resistance is desired.
On the other hand, as a method for obtaining a rubber composition having a low heat buildup, there are generally known the method of using carbon black having a large particle size, the method of reducing the amount of the carbon black, etc., but in all of these methods, the breaking strength and wear resistance of the rubber falls, and therefore, they are not practical. Further, Japanese Examined Patent Publication (Kokoku) No. 59-2451 proposes the improvement in the heat buildup by using carbon black having a broad distribution of aggregate, but the effect of improvement cannot be said to be sufficiently practical yet and, also, the wear resistance is decreased.
As explained above, numerous proposals have been made to improve the heat buildup of rubber compositions, but no low heat buildup rubber composition which can sufficiently satisfy with the recent highly advanced needs for low fuel consumption tires has been obtained at the present time. Development of such a rubber composition is still extremely strongly desired.